In related developments, an international team of experts began investigating the virus's behavior in Saudi Arabia, according to a press report, and it came to light that US Health Secretary Kathleen Sebelius recently made an emergency declaration that paves the way for the use of new diagnostic tests for the virus.

The Saudi Ministry of Health (MOH) announced the new case in a typically brief statement this afternoon. The ministry said only that the case is in an 83-year-old man in Al-Ahsa governorate who has multiple chronic diseases. Al-Ahsa is the site of a recent hospital-centered cluster of 22 MERS cases, including 10 deaths.

The new case, not yet noted by the World Health Organization (WHO), apparently raises the unofficial MERS-CoV count to 55 cases with 33 deaths.

Yesterday news media reports from Italy quoted a physician in Florence, site of Italy's first three MERS cases, as saying that 10 asymptomatic people had tested positive for the virus. The reports said confirmatory tests were being done at the Superior Health Institute (Istituto Superiore di Sanita) in Rome. But today an official at the institute said none of those tests have been confirmed.

In comments to ProMED, the disease tracking service of the International Society for Infectious Diseases, Giovanna Rezza, MD, wrote, "With regard to rumours appeared on the press—and published on ProMED—about positivity for MERS-CoV among close contacts of confirmed cases detected in Florence, we would like to specify that the reference lab of Istituto Superiore di Sanita has not confirmed any of the samples from asymptomatic contacts of the cases.

"Moreover, the virus has not been characterized yet. Thus, significant mutations in the viral genome that might explain changes in virulence on transmissibility cannot be confirmed as yet."

In addition, a machine-translated media report from Italy quoted Rezza as saying that eight people who were in contact with MERS patients tested negative for the virus on a second test, although their first test results had been positive. The report identified Rezza as director of the institute's infectious diseases department.

The report of the asymptomatic cases followed news of Italy's first three MERS-CoV cases in the previous few days. The infection was confirmed on May 31 in a 45-year-old man who got sick after returning to Italy after a 40-day stay in Jordan. Two days later, authorities reported infections in his 2-year-old niece and a 42-year-old coworker.

The talk of asymptomatic cases has caused a stir because the possible existence of undetected mild or asymptomatic cases, with the potential for spreading the disease far and wide, has been one of the big question marks about the virus. More than half of the cases reported so far have been fatal. The three patients in Italy have been described as being in stable condition.

Meanwhile, a WHO-led team of experts arrived in Saudi Arabia, site of most of the known MERS-CoV cases, today to investigate the situation, according to a Canadian Press (CP) report.

WHO spokesman Gregory Hartl said the delegation hopes to shed light on where the virus hides in nature and how people are being exposed to it, as well as its severity spectrum, according to the story.

Keiji Fukuda, MD, the WHO's assistant director general for health security and the environment, is leading the team, along with Jaouad Mahjour, MD, MPH, director of communicable diseases at WHO's Regional Office for the Eastern Mediterranean, CP reported.

Hartl said the team numbers 10 to 15 people and includes experts from Canada, the US Centers for Disease Control and Prevention (CDC), the United Nations Food and Agriculture Organization, and the World Organization for Animal Health (OIE).

In other developments, Sebelius, secretary of the US Department of Health and Human Services (HHS), said in a May 29 statement that MERS-CoV poses "a significant potential for a public health emergency that has a significant potential to affect national security or the health and security of United States citizens living abroad."

"On the basis of this determination, I also hereby declare that circumstances exist justifying the authorization of emergency use of in vitro diagnostics for detection of . . . [MERS-CoV]" under section 564 of the Federal Food, Drug, and Cosmetic Act, Sebelius stated.

The statement does not mean that the United States faces a public health emergency with regard to MERS now, said Elleen Kane, a spokeswoman for the HHS Office of the Assistant Secretary for Preparedness and Response.

"The declaration was a necessary first step in the legal and regulatory process to allow FDA [the Food and Drug Administration] to issue an emergency use authorization for the use of new laboratory diagnostic test kits designed to detect the novel coronavirus," Kane told CIDRAP News by e-mail.

"Because this is a new coronavirus, a specific diagnostic had not been previously developed and cleared by the FDA for clinical diagnostic purposes. The EUA [emergency use authorization] allows CDC to share the coronavirus test kit domestically with qualified laboratories for clinical diagnostic use."

On Apr 19, Sebelius made a very similar declaration concerning the H7N9 influenza virus circulating in China, saying that circumstances justified the emergency use of in vitro diagnostic tests.